U.S. Pat. No. 6,901,729, is incorporated herein by reference in its entirety. This patent describes a header flotation system that is referred to as “non-independent”. Provisional Application Nos. 60/699,610, and 60/699,489, filed Jul. 15, 2005, are also incorporated herein by reference in their entirety.
A windrower typically consists of a self-propelled tractor or similar vehicle, and a cutting mechanism which is either towed by the tractor or carried thereby. The cutting mechanism carried by a windrower is typically referred to as a header, and is supported on the windrower by forwardly projecting arms. Briefly, the arms comprise elements of a lift and flotation mechanism or mechanisms operable for setting a height of the header above the ground or other surface over which the windrower moves, the flotation permitting the header to ride lightly up and over rises in the terrain during field operation.
Headers are typically available in a variety of configurations. Common elements of different headers include cutters operable for severing crops from the field. One typical cutting mechanism is a sickle cutter which includes a row of knives which extend across the width of the header and which are powered to move reciprocally sidewardly relative to a sidewardly extending array of fixed knives or bars, thereby effecting a cutting action. It is typically desirable for the cutters to operate at a constant speed, but, in operation, the cutting speed may vary as a result of changing conditions such as crop population, contact with the ground, or the like.
The sickle cutters may be accompanied by a reel disposed thereabove and rotatable for engaging the crop before cutting or other treatment, as is well-known in the art. It is of value to have a capability of varying the rotational speed of the reel versus ground speed to accommodate changing and different conditions, particularly crop conditions. In this regard, it is well-known to provide a capability for an operator to dial in a speed in revolutions per minute (rpm) using a speed selector dial, and for the reel to be rotated at the selected speed. A windrower may have the capability to be used with any of several headers, and the power required for driving the reel of a particular header at a selected speed may differ from that required for driving the reel of a different header.
A reel can be driven using a fluid drive, such as a fluid power takeoff (PTO), or a dedicated reel drive, of a windrower. A pump driven by the engine of the tractor provides pressurized fluid to the PTO system. The pump can be of a fixed displacement, the speed and direction of operation of the reel being controlled by one or more proportional solenoid controlled valves. Varying electrical current signals would be utilized for operating the solenoids, for rotating the reel at the desired speed and in the desired direction, and the electrical current required for driving the reel at a selected speed would need to be known, such that the controller controlling the solenoids can apply the correct current responsive to an operator command for achieving a selected speed. Reel speed will typically fall within a range between about 100% of the ground speed of the windrower, and 130 to 140% thereof.
It would be desirable to have an apparatus and method which enables varying the reel speed versus ground speed, particularly for varying reel speed within the range set forth above of between about 100% and 130 to 140% of ground speed. Additionally, it would be desirable to have an apparatus and method automatically operable for maintaining the reel speed at a selected percentage of ground speed during operation wherein the ground speed is varying. Further, it would be desirable to have an apparatus and method for automatically controlling reel speed, wherein the reel speed is not allowed to fall below a minimum value, even though the ground speed is decreased significantly, for instance, when the windrower is being slowed significantly for turning, or the like, such that when a stand of crop is contacted by the reel, the reel will not be moving so slow as to tend to push the crop away from the header.